Narciso Conteras 'cloned' other parts of the image to obscure the video camera that is visible above, but removed below.

AP: Narciso Conteras

A Pulitzer Prize-winning photographer has been sacked by the Associated Press (AP) news agency after doctoring a photo that he took while covering the Syria conflict last year.

AP says Narciso Conteras recently approached his editors and admitted to altering a photo of a Syrian rebel fighter to remove a journalist's video camera from the corner of the frame.

Director of photography and vice president Santiago Lyon says AP has ended its relationship with Conteras and will remove all of his photos from their archive.

"Deliberately removing elements from our photographs is completely unacceptable and we have severed all relations with the freelance photographer in question," he said in a statement.

"He will not work for the AP again in any capacity."

Conteras was one of five AP journalists who won a Pulitzer for their coverage of the Syrian conflict in 2013, although the photo in question was not part of the award-winning work.

He says he "cloned" other parts of the image in order to obscure the video camera in the corner of the photo, which he thought might be distracting for readers.

"I took the wrong decision when I removed the camera ... I feel ashamed about that," he said.

"You can go through my archives and you can find that this is a single case that happened probably at one very stressed moment, at one very difficult situation, but yeah, it happened to me, so I have to assume the consequences."

Mr Lyon says AP editors went back through all the photos Conteras had filed since 2012 and it agreed that none of them had been altered.

Nevertheless he said the matter had to be dealt with according to the agency's News Values and Principles, which states photos "must always tell the truth. We do not alter or digitally manipulate the content of a photograph in any way. No element should be digitally added to or subtracted from any photograph."

"It's very important for the AP to be completely transparent about things of this nature," Mr Lyon said.

Most news agencies allow photographers to use software to lighten or darken photos slightly, but not to add or remove parts of the image.